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    Creatinine Clearance (Cockcroft-Gault Equation)

    Calculates CrCl according to the Cockcroft-Gault equation.
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    When to Use
    Pearls/Pitfalls
    Why Use
    • Assessing a patient's renal function.
    • Prescribing a drug that is renally metabolized.

    From Dan Brown, PharmD, at Palm Beach Atlantic University, the primary author of the functional range of creatinine clearance paper:

    “The Cockcroft-Gault equation remains the gold standard after almost 40 years, despite inaccuracies that arise from variations in body composition among patients. Those who understand potential sources of error can adjust accordingly.”

    • While the Cockcroft-Gault equation is the most well-known and frequently-calculated estimates of GFR (via Creatinine Clearance), other calculators have recently gained attention as better estimates, like the MDRD. (The latter have not been validated in acute renal failure, only patients with chronic kidney disease.)
    • Creatinine clearance is still used as the standard for drug dosing, instead of GFR.
    years
    lbs
    mg/dL
    The Cockcroft-Gault Equation may be inaccurate depending on a patient's body weight and BMI; by providing additional height, we can calculate BMI and provide a modified estimate and range.
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    Next Steps
    Evidence
    Creator Insights

    Advice

    After calculating a creatinine clearance, providers should consider calculating an actual GFR as well, to determine the staging/severity of a patient's chronic kidney disease.

    CKD stage GFR level (mL/min/1.73 m2)
    Stage 1 ≥ 90
    Stage 2 60 – 89
    Stage 3 30 – 59
    Stage 4 15 – 29
    Stage 5 < 15

    Formula

    Cockcroft-Gault CrCl, mL/min = (140 – age) × (weight, kg) × (0.85 if female) / (72 × Cr)

    Ideal body weight (IBW), Devine equation:

    • IBW, kg (male) = 50 + [ 2.3 × (height, inches – 60) ]
    • IBW, kg (female) = 45.5 + [ 2.3 × (height, inches – 60) ]

    Adjusted body weight (ABW), kg = IBW, kg + 0.4 × (actual body weight, kg – IBW, kg)

    Facts & Figures

    The most common formula for determining creatinine clearance, which estimates glomerular filtration rate (GFR); creatinine clearance may over-estimate GFR by 10-20%, but still remains the standard for drug dosing adjustments.

    Based on several papers and expert opinions, we provide adjustments to the Cockcroft-Gault equation based on body weight and BMI, as it appears to become less accurate in weight extremes (underweight and particularly overweight/obesity). As recommended by Brown et al and Winter et al, adjustments and estimates are made as follows:

    Underweight BMI <18.5 Calculation uses actual/total body weight (i.e., no adjustment)
    Normal weight BMI 18.5-24.9 Calculation uses ideal body weight, range uses actual body weight
    Overweight / obese BMI ≥25 Calculation uses adjusted body weight, range uses ideal body weight

     

    Dr. Donald Cockcroft

    About the Creator

    Donald W. Cockcroft, MD, is a professor of medicine at the University of Saskatchewan. He is co-chair of Airways Research Group and the chair of the Quality Assurance Committee. Dr. Cockcroft specializes in asthma practice and research.

    To view Dr. Donald Cockcroft's publications, visit PubMed

    Dr. Henry Gault

    About the Creator

    Henry Gault, MD, MSc, (d. 2003) was named professor emeritus in 1993 after nearly 20 years as a physician and professor at Memorial University of Newfoundland. He was also director for the Division of Nephrology at the General Hospital and of the Renal Laboratory. Dr. Gault was a pioneer in the field of nephrology and his work on urine enzymology was a major influence on the discovery of the diagnosis of the rejection of kidney transplants.

    To view Dr. Henry Gault's publications, visit PubMed